Cooling systems of laser ignition devices, which are based on liquid cooling, have the disadvantage that coolant flowing out of a cooling circuit of the cooling system, in particular water (leakage water), may flow into the cylinder shaft of the internal combustion engine and may even enter the combustion chamber during a change of the laser spark plug. The compression ratio is thus increased during operation of the internal combustion engine, since the coolant, in particular water, is understood to be incompressible, so that the internal combustion engine may be destroyed as a result of the leakage water (water hammer). The causes of the leakage water are generally leaky cooling water connections or installation errors.